| 摘要: | 水庫是水資源調配運用之重心，其蓄水容量越大，重要性相對越大。水庫主要功能係藉其庫容蓄洪濟枯，控制及調節河川流量，以減小豐枯水期可用水量之差異及達到枯水時期穩定供水之目的，而攔河堰則以取水為主要功能，兩者構成區域水源供應主要之水利設施。因此，水庫與攔河堰系統之出水量分析及運轉規線研訂係水資源開發及有效運用之主要依據。有關區域水庫與攔河堰聯合運轉優化之研究迄今仍為熱門且極具有挑戰性之研究方向及課題，不同於以往之研究，本研究主要特點係由應用的觀點出發，根據美國陸軍工程師團所提出水庫水位指標保持平衡之精神，提出「解析模擬」之構想，以解析方式推導公共給水標的水庫系統各種組成方式之放水量通式，據以建構系統出水量分析之核心部分。至於水庫運轉規線制訂優化之研究，由於台灣河川天然流量之豐枯變化甚劇，不容易預測，為使水庫運轉得到最佳的綜合效益，一般係根據出水量分析之結果，細部調整運用方式，尋求合理之運轉規則。惟受限於水庫與攔河堰系統聯合運轉之複雜及具多參數之特性，傳統優化法不容易對此類問題進行優化。本研究為克服傳統優化法所面臨且難以解決之維度障礙，選擇有別於傳統優化技巧且屬柔性計算之遺傳演算法，採用不同編碼、解碼方式及適合度，經遺傳演算程序自動優化得到一組最佳規線，使能兼顧模式演算精度與分析自動化之需求，具有工程實務應用之價值。 本研究獲致主要之成果，有： 1. 本研究針對公共給水標的水庫所提出之完整型並聯或串聯出水量分析模式，可減少模擬模式發展過程之困難；而簡化型虛擬等量水庫串聯模式，則可大幅度減輕模式修改與驗證工作之負荷。根據模擬演算結果，因簡化所致之最大誤差僅4.08％，適用於水資源初步規劃。 2. 水庫與攔河堰組成之川流與水庫系統運轉，應優先運用水庫下游未控制流量，不足時才由水庫放水供應，如此可有效運用水資源，大幅提高系統出水量。至於水庫不同組成方式，串聯系統有別於並聯系統，最主要特性係各座水庫之入流量均源自同一水源頭，河川流量之時間序列分布相差不大，而且下游水庫之入流量為上游水庫之洩放水量及水庫間側向流量之和。因此，以公共給水標的而言，水庫串聯系統之最佳運轉方式係優先運用下游水庫之蓄存水量，以供應需求量，若不足供應時，才利用上游水庫之蓄存水量，如此可降低下游水庫發生無效溢流機會，減少水資源之浪費；而水庫並聯系統則以採用水庫水位指標相等之運轉方式為最佳策略。 3. 根據本研究之出水量分析結果顯示，水資源開發應不以開發大型水庫為起點，而以開發小型水庫與攔河堰為開端；再者，各水源設施宜予聯合運轉操作，以提升有限水資源之運用效率，換言之，現有水資源設施之單獨運轉宜逐漸被聯合運轉操作所取代。傳統之水庫年運用率（即年總出水量對水庫有效容量之比率，Y/TV）若大於1.0即認為其係水文上屬可行之水庫開發方案；惟若加入越域引水之設施及同時取用蓄水壩至下游引水堰間之流量，則前述之（Y/TV）大於2.0，應不足為奇。越高之（Y/TV）值表示系統之水資源開發效率及效益愈高。 4. 由於多座水庫系統聯合運轉之運轉方式不同，以致庫水蓄放的時間上分布有所變化，惟水庫系統整體調蓄功能可予提高。在某一規劃條件下，水庫規線係水庫管理者運轉操作之準則及依循，以獲得系統最佳效益。因此，研訂適當之聯合運轉規線除可減少水庫系統缺水量及缺水集中情形外，並可提高水力發電廠之發電效益。 5. 有關水庫規線研訂自動化之研訂，本研究首先提出之水庫規線編碼、解碼方式及遺傳演算優化程序之目標函數，均有實務應用價值。根據數值試驗結果顯示，依不同之目的，採用不同之目標函數值，例如(1/SI)、(1/SI+系統發電總量)或(1/SI+系統發電總量+(100-最大缺水率)) ，作為GA適合度函數值，均可自動得到滿意之規線。 6. 目前為減輕水庫興建對環境生態之衝擊，均保留環境與生態所需之各種水量，例如河川基本放流量、下游河道滲漏量等。其中河川基本放流量係為河川魚類與其他水生動物生態保育所洩放之水量，而河道滲漏量則係為不影響原有之地下水補注量而洩放之水量。根據研究結果顯示，河道之滲漏總量不僅受逕流總量之影響，亦受逕流量時間分布之影響，即流量分布愈均勻愈有利於滲漏。因此，興建水庫對下游河道之滲漏非一定有負面影響，只要水庫適當運轉，發揮調節流量作用，亦可產生正面影響。 7. 本研究提出「可視化模擬」之主要目的係供分析者直接在螢幕上經由圖表形式顯示試誤之過程與結果，例如在螢幕上以滑鼠牽引之方式調整水庫規線，於調整規線之同時即可見水庫水位歷線之變化，俾據以研訂最適宜之規線。因此，數字不再只是數字，更將其所代表之物理意義直接展現於螢幕上，使用者很快且很便利地取得決策分析所需之相關資訊，可有效的減少試誤過程。 Generally, a water resources system consists of two major facilities :(1) reservoir; (2) barrage. The reservoir is to regulate the variability of surface water flow and make water available when it is needed, and the barrage is used to divert water through the stream. Study on the firm yield analysis and operating rule curves for such a system will provide a long-term guideline for reservoir system operation. Optimization of water resources planning and management was studied in the last four decades, however, the topic is still a formidable challenges to water resources planner. The major advancement in this thesis, compared with previous studies, is to provide analytic solutions for reservoir releases in firm yield analysis on regional multireservoir and barrage systems. Furthermore, a GA (genetic algorithms) search technique is proposed to find a set of rule curves by using different approaches in coding and decoding. According to several numerical experiments on case studies reveal that automated model for rule-based operation can overcome computationally intractableness due to curse of dimensionality for reservoir operation problems in real world. The study attaines the following findings and conclusions: 1. A complete simulation model for a reservoir system operation can quickly reveal various factors influencing operation efficiency of the system, and can reduce the difficulties previously encountered. Meanwhile, a pseudo tandem reservoir model was developed to enhance the convenience of model modifications and calibrations. The maximum deviation of the simplification is only 4.08%, therefore, the simlified model is valid for preliminary planning . 2. For a reservoir-river system with its water abstraction point at an intake downstream of the dam, streamflow controlled by the dam can be utilized to significantly increase the water yield of the system. If more than one reservoirs in upstream, joint operation will make more efficient due to the complement by each others. Regarding reservoirs in series, the inflow of a downstream reservoir is the released amount of the upstream reservoir plus the lateral flow between those two reservoirs, and varies with the operation strategies of the upstream reservoir. As those reservoirs have almost the same source of water, the time distribution of inflows of reservoirs is nearly the same. This is the major difference between tandem and parallel reservoir systems. The results of this study indicate that operation of a multireservoir system in series has an efficient way to release for downstream reservoir with first priority for water supply purpose; For reservoirs in parallel, a strategy called balanced level indices (BLI) is verified to be the best for operating the multireservoir system with a water-intake located in the downstream of the confluence of all the related rivers. 3. Joint operation of reservoirs and barrages can enhance operation efficiency for water-supply. To reduce its impacts on environment, ecology and culture, development of water resources should start from building small scale dam incorporated with barrage rather than building a large dam. Traditional yearly reservoir utilization ratio, i.e. the ratio of the yearly firm yield and reservoir effective volume(Y/TV), greater than 1.0 represents a hydrological feasibility for dam construction. But, in the case of joint operation of multireservoir and barrages, the ratio is usually larger than 2.0, and means a high development efficiency. 4. Although each reservoir storage level varies with different operation strategies in a multireservoir system, the total storage function rises due to system joint operation. In order to gain the highest benefits, the system operation needs to obey rule curves. Therefore, deriving a proper rule curves can not only reduce the shortage amount and duration for downstream demand but also enhance hydropower efficiency. 5. Related to the optimization of reservoir operating rules, this study presents a new procedure to find a set of rule curves by different approaches in coding , decoding and choosing objection function . Those objection functions such as (1/SI), (1/SI+hydropower) and ((1/SI+hydropower)+(100-percentage of maximum shortage ratio)), employed to the fitness function of GA, resulted in a set of satisfied rule curves. 6. Nowadays, there is a trend to remain minimum instream flow discharge and the required water riverbed percolation in the downstream of a dam. The minimum instream flow is released for aquatic species and downstream riverbed percolation for recharging groundwater aquifer. The results of present studies reveal that the amount of downstream riverbed percolation is affected by not only the total amount but also the temporal distribution of stream discharge. The paper confirms that appropriate policy for reservoir operation can enhance total amount of riverbed percolation. 7. Because computations of the water yield involves a lot of cumbersome and time-consuming, a visual simulation model developed by Microsoft Visual Basic is presented to reduce the numbers of trial and error and the analysis time for firm yield in multireservoir-river systems. |
